The present invention relates to a method for making a first object which can be fixed with great accuracy in regard to its position in contact with a second object, and to an apparatus having a first object which can be fixed with great accuracy with regard to its position in contact with a second object.
In particular the present invention relates to a receiving device or pallet on which a workpiece can be clamped, and which can be fixed with great accuracy in its geometrical position in contact with a machine table of a machine tool.
The applicant's German Federal Gebrauchsmuster 87 01 619.2 there is already disclosed an apparatus for the repeatable, very precise fixing of the geometrical position of a first object with respect to a second object, in which the first device is especially in the form of a pallet bearing a workpiece and the second object in the form of a support or table of a machine tool. The pallet has a number of centering tenons disposed in one plane and spaced apart from one another at uniform angles in the plane, which upon the placement of the pallet against the support or machine table produce, with matching recesses int he support or table, a highly precise fixation of these parts with respect to one another. Both the pallet and the support or table are made from a high-quality machine steel. Since even in high precision machining of the pallet as well as the machine table slight departures of the centering tenons from the position of the recesses in the machine table are inevitable, provision is made in the known apparatus that the recesses in the support or table have lateral guiding walls provided with grooves, which when the centering tenons are introduced into the grooves, separate in resilient contact with the centering tenons. The necessity of the guiding walls yielding resiliently in the micron range to compensate for deviations between an ideal position of the centering tenons of the pallet and the position actually reached in production requires, on the one hand, a relatively complex machine table. On the other hand, the production of the pallets, of which a relatively great number are needed for each machine, is relatively expensive on account of the need for complex machining of the machine steel. Another problem in the operation of the known apparatus arises out of the relatively great weight of pallets made from machine steel.
European patent 0 111 092 (Erowa) has already disclosed a machine table for machine tools having a receiver for pallets; the pallets have at least two centering tenons which, when the pallets are placed on the machine table, engage in recesses in a spring steel disk fastened to the machine table and separated from the latter vertically. The recesses are configured so that, when the centering tenons of the pallet are inserted into the recesses in the spring steel disk a vertical deflection of the marginal areas of the spring steel disk takes place after the centering tenons are inserted, so that the marginal areas of the spring steel disk are deflected horizontally backward simultaneously with the vertical deflection. Therefore the spring steel disk can compensate inaccuracies of the pallet in the positioning of its centering tenons in relation to one another as well as produce a centering of the position of the pallet in relation to the machine table. No information as to how any centering of the pallet with respect to the machine table can be achieved without this relatively complex spring steel disk can be found in this European patent.
The principle of centering a pallet on a machine table by means of a resilient element which engages centering tenons is long known in itself; as shown, for example, by German Patent 12, 57 496 which discloses as one embodiment of the resilient element a flexible wire clamped between flanges and bending horizontally and vertically, for engaging centering tenons. In this disclosure too it is obviously considered necessary to use separate spring elements for compensating inaccuracies between a fixed half coupling and a superimposable half coupling.